The present invention relates generally to communication systems and methods, and more particularly to optical communication systems and methods. Further, more specifically, the present invention pertains to optical communication systems and methods that employ wavelength division multiplexing.
Optical fiber has been widely accepted as an interconnection medium for communication networks, due mainly to the advantages offered by fiber, such as higher bandwidths and better noise performance, as compared to electrical media. Multi-channel optical networks allow several users to access the fiber simultaneously, thus increasing the overall network capacity. The optical bandwidth may be divided into several channels, each capable of transmitting non-interfering signals at distinct wavelengths, or in other words, wavelength division multiplexed (WDM).
Such an optical network can be used to optically connect any number of nodes having optical transceivers associated therewith. For example, an optical interconnect can be used to connect a plurality of processors for interprocessor communication (e.g., the communication of packets between one or more processor nodes of a network, such as a ring network, or a linear tapped bus network).
Switches used for such optical interconnect are generally constructed to operate as either a connection oriented or a connectionless oriented interconnect. In the case of a connection oriented interconnect, the switch connections between inputs and outputs are established by the user and the connections will remain until the user changes them. Therefore, they are considered connection oriented. The connection establishment commands by the user determine how input information is routed. In the case of a connectionless oriented switch, there are no connection establishment commands by a user. Instead, as each message is sent to the switch, header information associated with the message is read and the destination determined. In other words, the switch becomes responsible for the proper routing. Each message is self-routed, and is therefore, the switch is connectionless.
The optical fibers of at least certain conventional optical interconnects are coupled to the nodes of the network (e.g., processor nodes) through optical to electrical interfaces (e.g., optical transceivers), and interconnected generally at a centralized switch to accomplished desired routing of information. The centralized switch (e.g., a connectionless switch), for example, receives from the processor nodes (e.g., transmission nodes) information packets in the form of optical signals. The external central switch converts the optical signals to electrical signals, decodes the packet header to determine the destination node or nodes (e.g., processor node) for the information, converts the electrical signals back to optical signals, and routes the optical signals to the proper destination processor node.
In other words, generally, such conventional (e.g., connectionless) optical switches include optical-electrical-optical (OEO) design architectures. These architectures provide packet self-routing which is necessary for multiprocessing systems. However, the brute force method of optical to electrical, and thereafter, electrical to optical conversion, has a number of disadvantages. For example, considerable energy is dedicated to the optical to electrical and electrical to optical conversions, leading to higher power implementation. Further, for example, there is also an increase in the number of components because of the dedication of circuitry to perform the optical to electrical and electrical to optical conversion.
Due to the high module density, complex packaging, and higher power implementation of such OEO designs, reliability is negatively affected. Yet further, there is also a higher cost as a result of the high module density, complex packaging, and high power requirements. Still further, because all the optical fibers are routed to a centralized (e.g., external to the nodes) switch, a single point of failure for the optical network exists at the switch. The switch module may also need to be redesigned on an ongoing basis each time the data rate or data communication protocol changes.